Method of making seamless tubes



y 1932- J. J. DUNN 1,858,920

IETHOD OF MAKING ISEAMLESS TUBES Filed March '25, 1928 IIIIIIIIIIIIIIIIIIIIII I 176049723021: .1 .hr Du/v/v,

Patented May 17, 1932 UNITED STATES PATENT OFFICE JERRY JAY DUNN, 0E ELLWOOD CITY, PENNSYLVANIA, ASSIGNOB TO NATIONAL TUB! COMPANY, OF PITTSBURGH, PENNSYLVANIA, A CORPORATION OF NEW JERSEY METHOD OF MAKING SEAMLESS TUBES Application filed March, 1928. Serial no. 264,068.

-This invention relates to a methodof making seamless tubes of relatively large diameters, and has for its object the rovision of a novel method by which seam ess tubes of over five and one-half inches finished diam eter and less than one-half inch wall thickness may be commercially produced with a minimum amount of scrap. With the methods heretofore generally employed, the making of tubes of over five and one-half inches finished diameter and less than one-half inch wall thickness was commercially wasteful, due to the stresses which were set up in the metal. These stresses caused the metal to tear and open up and the tubes, thus damaged, formed scrap which was useless.

The method for making seamless tubes in general use in the United States, is to pierce a solid blank in a cross-roll machine, producing a tube somewhat less than one-fourth inch heavier than that of the finished wall desired; then rolling this heavy Walled tube in a groove and over a mandrel in a two-high rolling mill to reduce the wall thickness to the finished dimension; then passing the tube through a cross-roll machine for the purpose of removing the scratches left on the surfaces of the tube by the preceding operation,

rounding the tube and smoothing the surface generally; then sizing the tube.

An attempt has been made to modify thismethod so as to produce large diameter tubes as disclosed in the patent to Ralph C. Stiefel, No. 1.474.800. dated November 20, 1923'. In

this Stiefel patent the usual steps are carried out except that a portion of the work heretofore done in the piercing and rolling steps has been transferred to the cross-rolling step, where usually relatively little work is done. a

The method of this'Stiefel patent is objectionable due to the fact that too great an amount of work must be' done in the piercing operation" and. due to the fact that the diam eter of the pierced blank is reduced in the plug-mill operation, thereby increasing the amount of expansion that must be made in the cross-rolling operation and, since there isa limit to the amount of expansion that can be made in the cross rolling operation, the size or diameter of the tubes is limited.

The present method consists in piercing a solid heated blank by cross-rolling over a piercing plug so as to form a tubular blank materially longer and having a diameter slightly reate'r than that of the solid blank and a we 1 thickness of more than three times the thickness of the finished tube. During this piercing operation, the work is limited so that a line on the blank, or an element of its surface, will not be twisted or displaced a total, arithmetically added, an angle of twenty-five degrees; or, if the displacement is in one direction continuously, the total should not exceed eighteen degrees. This is an important limitation since, if the twisting of the metal is held approximately within these limits, the metal will not tear and the seams will not be opened. After being pierced, the tubular blank is then immediately passed, without reheating,

to a secondpiercing or cross-rolling, expanding operation. The once pierced tube is sufficlently hot to be easily worked and is subected to a second piercing or cross-rolling,

expanding operation by again cross-rolling metal.

T' 'The blank, after the second piercing or cross-rolling operation, is then passed immediately and without reheating to an expending, cross-rolling operation where it is cross-rolled over an expanding plug to reduce the. wall thickness from forty to sixty percent and to increase the diameter of the blank not less than thirty percent in reaching the diameterof the finished tube, or, if the tube is to be sized, to a slightly greater diameter than the diameter of the finished tube. The length of the tube is also slightly increased in this cross-roll, expanding operation. The tube blank has sufficient ductility when entering this last operation that it will withstand more twist without tearing than it will in the piercing operations. Therefore, the work in the cross-roll,;.expanding operation is controlledso as to prevent-the twisting or displacement of a line on the blank or an element of itssurface more than thirty-five degrees.

The tube, as produced by this last crossrolling and expanding step, is suitable for use as a hot finished seamless tube. However, if desired, it may be passed through the well known reeling and sizing rolls to smooth and reduce it to exactly the desired diameter. WVheresuperior finish is desired, the hot finished tube produced by the above described operations may. be cold drawn in the usual way.

It will also beunderstood that I do not wish to be limited tothe single expanding, cross-rolling operation since, when it is desired to produce some sizes of tubes, it may be necessary or desirable to use two or more expanding, cross-rolling operations, in which case the tube will preferably be reheated after the first expanding, cross-rolling operation. It may also be desirable, when producing extremely thin-walled tubes, to re heat the blanks after the second piercing or V cross-rolling operation and, therefore, I do not wish to be limited to expanding without reheating. I A particular advantage is gained by the method of this application in that the diameter of the blank is increased at each operation, and also by the fact that only three passes are generally necessary to produce a hot finished tube while, in the methods of the prior art in which plug-mills are used to reduce the wall thickness, the diameter of the blank is reduced and several passes are required in the plug-mill which cools the tube to'such a degree that the work of the expanding cross-rolls is limited.

In the drawings: Figure 1 is'a diagrammatic view showing the first piercing operation.

Figure 2 is a similar view showing the second piercing or cross-rolling operation.

Figure 3 is a similar view showing the expanding operation.

Referring more particularly to the drawings in which the apparatus. is diagrammatically shown performing the steps of this invention, the letter A designates the solid heated blank which is being pierced in a standard piercing mill composed of crossrolls 2 and a piercing plug 3. The rolls 2'are provided with the usual pass and serve to force the blank over the piercing point 3 so rolls 5 areprovidedwith the usual pass and serve to force the tubular blank over the piercing point (5so as to again pierce or expand the blank and reduce its wall thickness materially,tliusforming a tubular blank having a materiallygreater diameter and thinner wall than the blank produced in the first piercing operation.

The work in each of the above piercing operations is limited so as not to twist the metal blank a sulficient amount to tear or rupture the metal and yet is suiiiciently heavy so as to produce a blank, after the second piercing operation, having a wall of approximately twice the thickness of the wall oi the finished tube. v I

Experience hasshown thatthe work in the first piercing operation should be limited so as not to twist al ine on the blanlcor an element of its surface in one direction continuousl Y more than 18 degrees, while the work in tie second piercing operation should be limited so as not to twist a line on the'blank or an element'of its surface in one direction more than 15 degrees, so as to prevent tearing orrupturing oi the metal.

The blank C produced by the second piercing operation is passed. immediately, without reheatingufrom' the second piercing operation to a cross-rolling and expanding mill, shown in Figure hand composed of crossrolls 8 and an expanding plug 9 of standard design. The rolls 8 are provided with the usual pass and serve to force the blank C over the expanding plug 9 so as to expand the blank more than thirty percent and, at the same time, reduce the wall thickness from 40 to 60 percent, thus forming a relatively thin-walled large diameter tube in three crossroll passes.

The work of the cross-rolling and expand ing mill is limited orcontrolled soas not to twist a line on the blank or an element of its surface in one direction more thani35 degrees so as to prevent tearing orrupturing of the metal in this last pass.

'By utilizing the three cross-rolling operations, as above described, by which a tube is formed in the first operation and the tube is expanded and its wall reduced in each of the other'two operations, I am enabled to materially reduce'the number. of passes over the number ofPasses necessary when a plugmill is used't-d reduce the wall thickness and, therefore, the tubular blank is delivered to the last expanding operation sulficiently hot changed without departing from the scope of my invention as defined in the appended claims.

I claim 1. The method of making large diameter seamless tubes which consists in piercing a solid heated blank by cross-rolling over a piercing plug to form a tubular blank having a diameter slightly greater than that of the solid blank and a wall thickness less than twenty percent of the outside diameter, then subjecting said tubular blank without reheating to a second piercing operation by crossrolling over a piercing plug to very materially increase the diameter and length and decreasethe wall thickness of the blank, and then subjecting the tubular blank resulting from said second piercing operation without reheating to a cross-rolling operation over an expanding plug so as to reduce the wall thickness not less than forty and not more than sixty percent of the wall thickness of the tubular blank resulting from the second piercing operation and also cause a relatively large increase in the'diameter of the tube and a relatively slight increase in length.

2. The method of making large diameter seamless tubes which consists in piercing a solid heated blank by cross-rolling over a piercing plug to form a tubular blank having a diameter slightly greater than that of the solid blank and a wall thickness less than twenty percent of the outside diameter, then subjecting said tubular blank without reheating to a second piercing operation by crossrolling over a piercing plug to very materially increase the diameter and length and decrease the wall thickness of the blank, and then subjecting the tubular blank resulting from said second piercing operation without reheating to a cross-rolling operation over an expanding plug so as to reduce the wall thickness not iess than forty and not more than sixty percent of the wall thickness of the tubular blankresulting from the second piercing operation, increase the diameter of the tube not less than thirty percent of the diameter of the tubular blank resulting from the second piercing operation, and also caus versely proportional to the change in its cross-sectional area.

3. The method of making large diameter seamless tubes which consists in piercing a solid heated blank by cross-rolling over a piercing plug to form a tubular blank having a diameter slightly greater than that ofthe solid blank and a wall thickness less than twenty percent of the outside diameter, then subjecting said tubular blank to a second piercing operation by cross-rolling over a piercing plug to very materially increase the diameter and length and decrease the wall thickness of the blank, and then subjecting the tubular blank resulting from said second piercing operation to a cross-rolling operation over an expanding plug so as to reduce 1 the wall thickness not less than forty and not more than sixty percent of the wall thickness of the tubular blank resulting from the second'piercing operation and also cause a relatively large increase in the diameter of the tube and a relatively slight increase in length.

4. The method of making large diameter seamless tubes which consists in piercing a solid heated blank bycross-rolling over a piercing plug, controlling the work in said cross-rolling operation so as to prevent the twisting of a line on the blank in one direction continuously more than 18 degrees and to form a tubular. blank having a diameter slightly greater than that of the solid blank and a wall thickness of more than three times the thickness of the wall of the finished tube,

then subjecting said tubular blank without reheating to a second piercing operation by cross-rolling over a piercing plug, controlling the work in said cross-rolling operation so as to prevent the twisting of a line on the tubular blank in one direction continuously more than 15 degrees and to very materially increase the diameter and length of the tubular blank and to decrease the wall thickness of the blank to approximately twice the thickness of the wall of the finished tube, and then subjecting said tubular blank without reheating to a cross-rolling operation over an expanding plug, controlling the work in said cross-rolling operation so as to prevent the twisting of a line on the tubular blank in one direction more than 35 degrees, reduce the wall thickness not less than forty and not more than sixty percent of the wall thickness of the tubular blank, increase the diameter of the tubular blank not less than thirty percent, and also causing a change in the length of the blank inversely proportional to the change in its cross-sectional area.

5. The method of making large diameter seamless tubes which consists in piercing a solid heated blank bv cross-rolling over a piercing plug, controlling the Work in said wcross-rolling operation so as to prevent the mg a change in the length of the tube in-' twisting of a line on the blank in one direction continuously more than 18 degrees and then subjecting said tubular blank to a second piercing operation by cross-rolling over a piercing plug, controlling the work in said cross-rolling operation so as to prevent the twisting of a line on the tubular blank in one direction continuously more than 15 degrees and to very materially increase the diameter and length of the tubular blank and to decrease the wall thickness of the blank to approximately twice the thickness of the wall of the finished tube, and then subjecting said tubular blank to a cross-rolling operation over an expanding plug, controlling the work in said cross-rolling operation so as to prevent the twisting of a line on the tubular blank in one direction more than 35 degrees, reduce the wall thickness not less than forty and not more than sixty percent of the wall thick ness of the tubular blank, increase the diameter of the tubular blank not less than thirt-y percent, and also causing a change in the length of the blank inversely proportional to the change in its cross-sectional area.

6. The method of making large diameter seamless tubes which consists in piercing a solid heated blank by cross-rolling over a piercing plug to form a tubular blank having a diameter slightly greater than that of the solid blank and a wall thickness less than twenty percent of the outside diameter, then subjecting said tubular blank to a second piercing operation by cross-rolling over a piercing plug to very materially increase the diameter and length and decrease the wall thickness'of the blank, and then subjecting the tubular blank resulting from said second piercing operation to a cross-rolling operation over an expanding plug so as to reduce the wall thickness not less than forty and not more than sixty percent of the Wall thickness of the tubular blank resulting from the second piercing operation and also cause a relatively large increase in the diameter of the tube and a relatively slight increase in length.

7 The method of making large diameter seamless tubes which consists in piercing a solid heat-ed blank by cross-rolling over a piercing plug to form a tubular blank having a diameter slightly greater than that of the solid blank and a wall thickness less than twenty percent of the outside diameter, then subjecting said tubular blank to a second piercing operation by cross-rolling over a piercing plug to very materially increase the diameter and length and decrease the wall thickness of the blank, and then subjecting the tubular blank resulting from said second piercing operation to a cross-rolling operation over an expanding plug so as to reduce the wall thickness not less than forty and not more than sixty percent of the wall thickness of the tubular blank resulting from the second piercing operation, increase the diameter or" the tube not less than thirty percent of the diameter of the tubular blank resulting from the second piercing operation, and also causing a change in the length of the tube inversely proportional to the change in its crosssectional area.

8. The method of making large diameter seamless tubes which consists in piercing a solid heated blank by cross-rolling over a piercing plug, controlling the work in said cross-rolling operation so as to prevent the twisting of a line on'the blank in one direction continuously more than 18 degrees and to form a tubular blank having a diameter slightly greater than that of the solid blank and a wall thickness of more than three times the thickness of the wall of the finished tube, then subjecting said tubular blank to a second piercing operation by cross-rolling over a piercing plug, controlling the work in said cross-rolling operation so as to prevent the twisting of a line on the tubular blank in one direction continuously more than 15 degrees and to very materially increase the diameter and length of the tubular blank and to decrease the wall thickness of the blank to approximately twice the thickness of the wall ot'the finished tube, and then subjecting said tubular blank to a cross-rolling operation over an expanding plug, controlling the work in said cross-rolling operation so as to prevent the twisting of a line on the tubular blank in one direction more than 35 degrees, reduce the wall thickness not less than forty and not more than sixty percent of the Wall thickness of the tubular blank, increase the diameter of the tubular blank not less than thirty percent, and also causing a change in the length of the blank inversely proportional to the change in its cross-sectional area.

In testimony whereof, Ihave hereunto set my hand.

J. JAY DUNN. 

